This invention relates to sheet carriers that are normally hand held and used, for example, at a construction job site, for carrying sheets of plywood, wallboard and the like sheet material from one place to another.
Those familiar with modern residential and commercial structures are aware of the wide use of sheets of plywood and wallboard in the design and construction of such structures. Such sheets of materials as received from the supplier are usually stored at one location at the job site. Thereafter, as the needs arise at the job site, the sheets are distributed to the various points at which they are contemplated for use or embodiment in the structure.
This distribution of the sheet material is usually done by a worker who, alone or with the aid of another worker, simply carries the sheets, usually one at a time, from the storage location to the various points of contemplated use or embodiment in the structure. The sheets are frequently heavy, and are commonly large (usually 4'.times.8'), thus making it difficult and awkward for a worker to grasp and, without aid, manipulate and carry over and about the many obstructions that exist at a construction job site. As such, most of such sheet distribution is performed by workers that work in pairs and who cooperate in lifting and carrying each sheet to its point of ultimate use at the job site.
Several devices have been proposed for use as hand held sheet carriers for use by a single worker and without the aid of another worker for carrying such sheets about a job site area. In general, such devices suffer from one or more disadvantages that have detracted from their gaining wide acceptance in the market place.
In many cases, the devices are only capable of being used satisfactorily to handle and carry the sheets under optimum conditions, such as those encountered when the terrain being traversed is horizontal and unobstructed, such devices being otherwise incapable of performing satisfactorily, for example, when the need arises to traverse a stairway or other inclined pathway. In general, devices which are only satisfactorily used in unobstructed level areas cause damage to the sheets if used to carry the sheets on inclined pathways, or otherwise require more effort to overcome the problems encountered during use on such inclined pathways than is required to simply handle the sheets by hand.
Apart from the above, most of the known sheet carriers are so constructed that it is difficult for a worker to position the sheet on the carrier in preparation for its being lifted and carried about at the job site by the worker without first having to lift the sheet with one hand and simultaneously orient the carrier with reference to the bottom edge of the sheet by means of the other hand. This is a task requiring considerable effort as will be apparent to those encountering such tasks, and not infrequently the sheets are damaged during the preparatory procedure.
Most of the proposed devices have a sheet support portion or member which is adapted to straddle the lower edge of the sheet and a handle which is usually integrally joined thereto or so designed as to be fixed with respect to the support member during use of the carrier. The sheet support member of the carrier is normally oriented along the center line of gravity for the sheet when the sheet is being carried on a horizontal surface, and the handle of such devices under such circumstances is located above the sheet support member. Provisions are usually made in the design of such carrier devices to hold the handle apart from the sheet so as to avoid an abrasive action on the hand knuckles during use.
Such devices as are provided with a handle that is either integrally joined or otherwise fixed relative to the sheet support member suffer from the disadvantage that they are difficult to use in carrying the sheets on inclined passageways such as on inclined ramps and stairways. In such cases, there is a need to carry the usually eight foot long sheet at a substantial angle to the horizontal as the worker traverses the stairway or ramp. This causes both the handle and center line of gravity to shift rearwardly relative to the support member when the sheet is tilted during an ascent of a stairway or forwardly when the sheet is tilted during a descent of a stairway. Since the lifting forces which support the sheet and carrier are applied vertically through the handle, there is a moment of horizontal force under such circumstances which tends to counteract the tilting movement of the handle and which, as such, tends to disrupt the seating arrangement between the support member of the carrier and the lower edge of the sheet. As a result, there is a tendency either for the sheet to slide on the support member so that extreme effort is required to retain the sheet in place, or for the support member to tilt relative to the edge of the sheet and thereby dig in and damage the sheet along its lower edge, all of which is unsatisfactory and detracts from the wide use of such devices. To prevent such sliding or tilting movement while traversing a stairway requires considerable effort and strength on the part of a worker, and, as such, there is a reluctance to use such devices where traversal of an inclined path must be undertaken. Typical devices of this type are shown in the following U.S. Pat. Nos. 4,098,442 (Moore), 4,113,160 (Spiers), 4,177,911 (Griffin) and 4,190,278 (Jancik, Jr.).
Still other devices for use as sheet carriers have overcome this sheet sliding and damage problem by providing a simple pivotal connection between the sheet support member and the handle structure. This enables the sheet support member to pivot relative to the handle as the sheet is tilted to facilitate ascending or descending an incline and avoids the application of a horizontal moment of force to the sheet support member of the carrier device for reasons of a horizontal shift in location of the handle of the carrier. A typical device utilizing the pivotal concept is shown in U.S. Pat. No. 2,428,941 (Packard).